The huge underground defence system of the casemates is closely linked to the history of the City of Luxembourg. During the long building process, which itself lasted almost 150 years, the fortified city changed into a fortress. At the end of a siege led by Vauban, France took the Luxembourg fortress in 1684 on behalf of French King Louis XIV. Vauban then planned and built an impressive defence complex that gave the city the epithet “Gibraltar of the North”. The remains of the fortifications have belonged since 1994, along with the old town, to the UNESCO World Heritage.